New monthly water use data for California water utilities shows that residential water use varies widely around the state, and that the response to the drought has been uneven. Moreover, in some areas, residential use averages more than 500 gallons per person per day, indicating that we could be doing much more to save water.
In July, the State Water Resources Control Board, or the Water Board, issued an emergency regulation to increase water conservation in urban areas. The new regulations prohibit certain water uses, like washing driveways and sidewalks, and imposed new restrictions on outdoor irrigation. Additionally, water utilities are now required to submit monthly reports on water use, including a comparison to how much water was used during the same month in 2013. Last week, the Water Board published the latest monthly water use reports for 397 urban water utilities. While a handful of utilities failed to report on time, those that did report cover about 99% of the state’s population.
Each water utility reports per-person water use in terms of gallons per-capita per day or “gpcd” and the portion used by residents in and around their homes. The result is a first of its-kind compilation of monthly water use data for urban water utilities in the state. And while officials cautioned that many factors affect water use, these data, displayed on the map below, reveal a number of interesting patterns and trends. Click on a utility’s service area to view a chart of residential water use, and how it compares to the same month last year, and to the average use for the state and its Hydrologic Region.
The Water Board collected information from all of the state’s “urban water suppliers” defined by state law (California Water Code Section 10617) as “a supplier, either publicly or privately owned, providing water for municipal purposes either directly or indirectly to more than 3,000 customers or supplying more than 3,000 acre-feet of water annually.”
We mapped water suppliers using information from the California Department of Public Health’s Drinking Water Systems Geographic Reporting Tool, supplemented by our own research. Where a water supplier serves a large, mostly rural area, we identified populated areas within the service area.
Perhaps the first thing you notice is the vast range in reported water use. Residential water use in September ranged from a low of 45 gpcd in Santa Cruz to a high of 584 gpcd in areas served by the Santa Fe Irrigation District in San Diego County. Water use tends to be lower in the cooler coastal region and in denser, urbanized areas. Likewise, water use tends to be higher in hotter, drier regions and in suburban areas with more outdoor landscaping and lawns. The chart below highlights utilities with the five highest and lowest residential per capita water use rates in the state.